A. Field of the Invention
The present invention relates to a moldable hydrophilic polymer composition, for use in a molding device preferably an injection molding device.
When in the following description the term is used hydrophilic polymers are polymers with molecular masses from approximately 10.sup.3 to 10.sup.7 Dalton carrying molecular groups in their backbone and/or in their side chains and capable of forming and/or participating in hydrogen bridges. Such hydrophilic polymers exhibit in their water adsorption isotherm (in the temperature range between approximately 0.degree. to 200.degree. C.) an inflection point close to the water activity point at 0.5. Hydrophilic polymers are distinguished from the group called hydrocolloids by their molecular dispersity. For the maintenance of the molecular dispersity of said hydrophilic polymers, a fraction of water--according to the working range of the present invention--of 5 to 25% by weight of said hydrophilic polymers must be included; provided that the temperature of said hydrophilic polymers is in the working range between 50.degree. C. and 190.degree. C. of the present invention.
There are other hydrocolloids, not hydrophilic polymers in the sense of this definition, which contain more or less spherical or fibrous particles whereby those particles are composed of several macromolecules of hydrophilic polymer within the molecular mass range of 10.sup.3- 10.sup.7 Dalton giving rise to particle sizes between 0.01-10 microns which is the typical range of colloidal particles. It is a primary object of the present invention to utilize hydrophilic polymer compositions in the production of capsules.
B. Description of the Prior Art
Capsule-making machines have been developed to utilize dip-molding technology. Such technology involves the dipping of capsule-shaped pins into a gelatin solution, removing the pins from the solution, drying of the gelatin upon the pins, stripping off the gelatin capsule parts from the pins, adjusting for length, cutting, joining and ejecting the capsules. Prior art capsule-making machines have utilized the combination of mechanical and pneumatic elements to perform these functions at speeds up to about 1,200 size 0 capsules per minute. While the above described apparatus is in general suitable for the intended purposes, it is desirable to produce capsules at considerably high speed, over 15,000 size 0 capsules per minute, while at the same time precisely controlling the properties of the gelatin in order to produce the capsules hygienically and with minimum dimensional deviations so that the capsules can be filled on high speed equipment.
A prerequisite for any material to be moldable by an injection process is its ability to pass a glass transition point at a temperature compatible with the thermal stability of the material and the technical possibilities of an injection molding device.
Shirai et al. in U.S. Pat. No. 4,216,240 describes an injection molding process to produce an oriented fibrous protein product. The fibrous product as obtained by this process, differs fundamentally from the transparent glass like material of the capsules obtained from the present invention. Furthermore to obtain a flowable mass for the molding process, the protein mixtures used by Shirai et al. have to be denatured and thus lose their capacity to undergo dissolution.
Nakatsuka et al. in U.S. Pat. No. 4,076,846 uses binary mixtures of starch with salts of protein materials to obtain an edible shaped article by an injection molding process. With the present invention shaped articles from protein material, preferably gelatin and other hydrophilic polymers can be produced without the addition of starch.
Heusdens et al. in U.S. Pat. No. 3,911,159 discloses the formation of filamentous protein structures to obtain edible products of improved tenderness. With the present invention shaped articles are produced without a filamentous protein structure.
The use of an injection molding device for producing capsules of gelatin and other moldable hydrophilic polymers with similar properties is new and has not been suggested in the technical literature.
The present invention distinguishes from the known as described above, by the nature of the compositions and by the recognition that gelatin and other hydrophilic polymers possess a dissolution point within a temperature range usable for an injection molding process, provided the water content of the gelatin and other hydrophilic polymers lies within a characteristic range, giving allowance to avoid any essential drying or humidification processes of the capsules.